Thermoelectric Generation

Catching heat is the purpose of every internal combustion engine ever developed. Anywhere you see a hear gradient (difference in temp) between two objects, there is energy flow available and energy to be captured. Think of it as a pre-charged battery. Warm ocean surface water vs cold subsurface, hot engine vs cold air etc. The problem is that small differences in temperature are hard to work with.

I received a link today from a reader I won’t name without permission, he linked to an article on what seems to be a breakthrough in thermoelectric generation.

The claim is:

“We anticipate the thermoelectric voltage using our design to be about 100 times larger than what others have achieved in the lab,” Stafford added.

Now thermoelectric completely stinks as a generator these days but a 100 times improvement is pretty substantial to say the least. I’m not enough of an expert on the cutting edge but if you want to even get 10 milliamps at 3 volts out of a $50 pieltier effect device, you had better have a hundred degrees of temp difference. I’m sure many people who read that will have corrections and additions, but that has been my experience.

10 Responses to “Thermoelectric Generation”

Jeff,
I didn’t find it convincing. First, they haven’t actually made anything. It’s all calculation (not that there’s anything wrong with that :).

Secondly, it seems unthermodynamic. They talk of molecule-thick layers. But as you said, the energy depends on the temperature difference between the electrodes, and you couldn’t get much over that distance. In fact, there’s a bind – thin for best electrical effect and low material cost, but thick to force the flux to cross a big temperature differential.

This is a common bind in waste heat proposals. Waste heat is waste, and you generally want it to go away. But recovery obstructs its exit, because you want the max temp diff across that part of the path.

Al S.said

There’s certainly potential for heat engines and thermoelectic systems of some types. The old soviet orbital military radars were supposed to be powered by (nuke-heated) thermionic emission devices, like stacked vacuum diodes; I suspect they would convert some of the gamma to electric power also, potentially with efficiencies greater than 50%. We aren’t talking waste heat recovery here, though.
And there are thermo-acoustic heat engines, for natural gas liquification and whatnot, that would save lotsa energy, if we ran ‘em on a heat source like a molten-salt nuke.

Steve Fitzpatricksaid

I’m with Nick on this one. They have made nothing physical (not even single molecules!). All they have is quantum chemistry calculations. I would not give this even a 10% chance of ever turning into something microscopic, never mind macroscopic. I am reminded of Maxwell’s demons and molecular one-way trap-doors….. which also ended up being nothing but imaginary. Don’t hold your breath waiting for a simple way to by-pass the well known limitations of thermoelectric devices.

Retired Engineersaid

Nuclear thermal power is used in most deep space probes. Too far for PV solar. Apollo left some similar devices on the Moon. But it doesn’t generate all that much power. Sterling engines run on heat. And need a rather large difference to do much of anything. So count me on the skeptic side of this one.

However, it is possible to make cold from hot, propane or LP gas powered refrigerators come to mind, in RV’s or remote cabins without electricity. So it may not be totally unreasonable to produce electric power this way. Thermal solar, perhaps using Sterling engines, does work.

Pieltier devices are useful for generating local cooling of small things. No moving parts, and lousy efficiency. I’ve used them to cool detectors. Generate power? Easier to push a wet string up a steep hill.

BillyBobsaid

John Msaid

Whew, that press release once again reinforces what I think should be rule number one for academic researchers:

Insist on review and veto power or you will end up sounding like an idiot!

“Could” make CFCs obsolete? Helloooo!

“You could just take a pair of metal electrodes and paint them with a single layer of these molecules,”

Oh sure, like falling off a log!

And the last line in the paper itself:

“The efficiency of PPE-based devices increases with ring
number and is only limited by the electronic coherence
length, suggesting that highly efficient molecular-based
thermoelectric devices may soon be realized.”